Anna University EE 1402 POWER SYSTEM PROTECTION AND SWITCHGEAR Unit I Question Bank

UNIT – I

PROTECTION AGAINST OVER VOLTAGES

PART – A (2 MARKS)

1. What are the causes over voltages on power system?

2. What is meant by voltage surge?

3. State the attenuation and distortion of traveling waves.

4. What are the causes of power frequency and its harmonic over voltage?

5. What is ground wire?

6. What is use of ground wire?

7. What is a protector tube?

8. Define basic impulse level.

9. Mention the various insulation levels in substations?

10. What is a surge absorber?

PART - B

1. (a) What are the causes of over voltage on a power system? (8)

(b) Why is it necessary to protect the lines and other equipment of the power system against over voltages? (8)

2. Describe the phenomenon of lightning. (16)

3. What protective measures are taken against lightning over voltages? (16)

4. (a) What is tower-footing resistance? (4)

(b) Why is it required to have this resistance as low as economically possible? (4)

(c) What are the methods to reduce this resistance? (8)

5. (a) What is necessity of protecting electrical equipment against traveling waves?(6)

(b)Describe in brief the protective devices used for protection of equipment against such waves? (10)

6. Describe the protection of stations and sub-stations against direct lightning stroke. (16)

7. Describe the construction and principle of operation of

(i) expulsion type lightning arrester, (8)

(ii) Value type lightning arrester. (8)

8. What is Peterson coil? What protective functions are performed by this device? (16)

9. Write short notes on the following.

(i) klydonograph and magnetic link (4)

(ii) Rod gap (4)

(iii) Arcing horns (4)

(iv) Basic impulse insulation level (4)

10. What are the requirements of a ground wire for protecting power conductors against direct lightning stroke? Explain how they are achieved in practice. (16)

11. Determine the inductance of Peterson coil to be connected between the neutral and ground to neutralize the charging current of overhead line having the line to ground capacitive of 0.15μf. If the supply frequency is 50Hz and the operating voltage is 132 KV, find the KVA rating of the coil. (16)

12. (a) Explain the term insulation coordination. (8)

(b) Describe the construction of volt-time curve and the terminology associated with impulse-testing. (8)

13. Explain the operation of various types of surge absorbers (16)